/Engine/Plugins/Experimental/LandscapePatch/Source/LandscapePatch/Public/LandscapeTexturePatch.h
Gives size in unscaled world coordinates (ie before applying patch transform) of the patch as measured between the centers of the outermost pixels. Measuring the coverage this way means that a patch can affect the same region of the landscape regardless of patch resolution. This is also the range across which bilinear interpolation always has correct values, so the area outside this center portion is usually set as a "dead" border that doesn't affect the landscape.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category=LandscapePatch) virtual FVector2D GetUnscaledCoverage() const